How do you know when you're about to get sick? Do symptoms hit you one by one and progress or do you normally wake up with a full-fledged cold?

One professor wants to create an algorithm for smartwatches that warns you of impending colds or infections or confirms that one is coming if you start to experience symptoms. Although most smartwatches can have health apps installed on them, presumably this would be like combining a sophisticated fitness tracker with the device because it will track your vital signs.

Michael Snyder, the chair of the genetics department at Standford University, and his team enlisted the help of 40 volunteers to show how the technology works. The group wore smartwatches that tracked their pulse and skin temperature for up to two years. The smartwatches recorded unusually high heart rates and sometimes warmer skin temperatures up to three days before the volunteer showed symptoms of a cold.

Snyder told NewScientist.com “Once these wearables collect enough data to know what your normal baseline readings are, they can get very good at sensing when something’s amiss. We think that if your heart rate and skin temperature are elevated for about 2 hours, there’s a strong chance you’re getting sick.”

When you make your annual trip to the doctor's office, the nurse is comparing your vital readings to national averages and the readings from your last visit. Snyder says it's better to compare abnormalities in your vital signs to your own daily average readings because it's a better indication that something is wrong.

Before collecting data from volunteers, Snyder noticed how helpful this technology could be because of a situation that happened to him. He wore seven sensors for a year to test their reliability and at one point the sensors showed abnormalities in his vital signs. His heart rate had increased, the temperature of his skin had risen, and the amount of oxygen in his blood had decreased.

Even though he felt fine, he thought he might have caught Lyme disease from a recent trip to a rural area. Then he got a mild fever so he asked a doctor to prescribe him doxycycline, an antibiotic used to treat Lyme disease. His symptoms disappeared within 24 hours and later on, tests confirmed that his self-diagnosis was accurate.

Snyder says smartwatches with the algorithm could help people be more proactive with their health. But a health professional told NewScientist.com that one concern is user error or the device giving false readings. Another professional said the device could cause anxiety and too many people rushing to the doctor who turn out to be fine. Plus, he says that knowing a cold is coming may not always help you avoid it.

There was a case last year when wearable tech did more than just predict an illness, it literally saved a man's life. The man was taken to the hospital because of a seizure and the doctors noticed he had an irregular and fast heartbeat. They needed to know if the condition was chronic or triggered by the seizure so that they could provide the best treatment.

Luckily, the doctors noticed he was wearing a Fitbit so they checked the app on his smartphone to see his heart rate activity. That data showed that the heart condition was caused by the seizure so they were able to perform a procedure that saved his life. This incident was the first time in medical history that information from a fitness tracker-smartphone system was used to assist in medical decision making.

Other than monitoring your health (or more recreational uses) wearable technology can also alert you when someone you love is in danger. Listen to the podcast below to hear how this technology can help you stay connected during an emergency.